Air Pollution: Types, Sources, and Effects

Air Pollution Types and Sources

Global vs. Local Pollution

• Two main global pollution problems:
  • Thinning of the ozone layer.
  • Climate change.
• Specific types of air pollution:
  • Local sources affecting ground-level health.
  • Examples include factory emissions.

Natural Sources of Air Pollution

• Pollen: Considered a pollutant, a particulate matter affecting allergies.
• Forest fires: Occur naturally from lightning strikes, releasing pollutants through combustion.
• Volcanic eruptions: Another natural source.
• Dust: Particulate matter blown into the air by wind and erosion.

Human-Caused Pollution

• Two categories:
  • Primary pollutants.
  • Secondary pollutants.

Primary Pollutants

• Emitted directly into the air from natural or human sources.
• Examples:
  • Carbon monoxide (CO).
  • Carbon dioxide ($CO_2$).
  • Sulfur oxides ($SO_x$).
  • Nitrogen oxides ($NO_x$).
  • Particulate matter (PM): Solid or liquid particles suspended in the atmosphere, not gases.

Secondary Pollutants

• Formed through chemical reactions in the atmosphere.
• React with each other or atmospheric components.
• Example: Acid Rain
  • Sulfur oxides (primary pollutant) react with water vapor to form sulfuric acid.
  • Sulfuric acid ($H<em>2SO</em>4$) is a secondary pollutant.
• Ozone ($O_3$)
  • Forms in urban areas as part of smog.
  • Ground-level ozone in the troposphere is harmful to lungs.
• Peroxyacyl Nitrates (PANS)
  • Components of smog.
  • Formed when Volatile Organic Compounds (VOCs) combine with nitrogen oxides ($NO_x$).
  • VOCs and $NO_x$ may be primary pollutants; PANS are secondary.
  • Toxic and mutagenic (mutate DNA).

Ground-Level Ozone Formation

• Nitrogen oxides ($NO<em>2$, $NO</em>3$) combine with VOCs (e.g., benzene).
• Reaction occurs in the presence of heat and sunlight.
• Common in areas with heavy vehicle traffic because $NO_x$ comes from car emissions.

EPA Criteria Pollutants

• Six pollutants the EPA monitors due to their impact on human health and environmental issues.

1. Particulate Matter (PM)

• Indicates particle size (e.g., PM10, PM2.5).
• Smaller particles are more dangerous as they can enter the lungs.
• Aerosols: Liquid or solid particles suspended in the air.
  • Includes dust, soot, pollen.
  • Secondary pollutants like sulfates and nitrates.
  • Emissions from combustion.
• PM10: Particles smaller than 10 microns in diameter.
• PM2.5: Particles smaller than 2.5 microns in diameter (more dangerous).

2. Sulfur Oxides ($SO_x$)

• Where x is the variable of how many oxygens are in the molecule
• Includes $SO<em>2$, $SO</em>3$, etc.
• SOx and NOx cause smog and acid rain.
• Corrosive but odorless.
• Contributes to smog (haze in the air).
• Forms sulfuric acid ($H<em>2SO</em>4$) when combined with water causing acid rain, lowering pH.
• Natural sources: volcanoes, sea spray, soil dust.
• Human sources: combustion of coal and oil.

3. Nitrogen Oxides ($NO_x$)

• Includes nitric acid and nitrogen dioxide.
• Contributes to smog, acid deposition, and ozone depletion.
• Mainly from combustion engines (cars, trucks).
• Specific source: Combustion of petroleum by cars, not just cars alone. Combustion is key. The same thing for combustion of coal for sulfur oxides

4. Carbon Monoxide (CO)

• One oxygen atom.
• Colorless, odorless gas produced by incomplete combustion of fossil fuels highly toxic and kills you quickly.
• Inhibits respiratory system by replacing oxygen in the blood.
• Red blood cells cannot differentiate between oxygen and CO.
• Asphyxiant: Causes suffocation from the inside.

5. Volatile Organic Compounds (VOCs)

• Not exactly a criteria pollutant, but combines with $NO_x$ to form ozone at ground level.
• Component of photochemical smog.
• Examples: methane, propane, octane.
• Volatile: Evaporates easily. Organic: Contains carbon and hydrogen.
• Ozone is a criteria pollutant resulting from the combination of $NO_x$ and VOCs.
• Toxic at ground level in the troposphere.
• Damages lung tissue.

6. Lead (Pb)

• Heavy metal that damages the nervous system, including the brain.
• Can be an air pollutant as particulate matter.
• Sources: Burning leaded gasoline (banned in 1976), smelting of metal, contaminant in coal.
• Highly toxic and bioaccumulates in the body.
• Causes brain damage, developmental damage in children, and death.
• Lead in paint was legally lowered in 1970.

Factors Affecting Pollutant Impact

• Concentration: How much of the pollutant is present.
• Residence Time (Persistence): How long the pollutant remains in the atmosphere.
  • Short residence time: Localized effect.
  • Long residence time: Widespread or global effect.

Effects of Air Pollution

• Human Health
  • Chronic: Long-term effects (e.g., asthma from smog exposure).
  • Acute: Immediate danger (e.g., carbon monoxide poisoning).
  • Carcinogenic: Linked to causing cancer.
  • Mutagenic: Messes with DNA.
• Economic Effects
  • Damage to agriculture: Affects plant health, crop yields, and soil quality.
  • Damage to forests: Impacts the timber industry.
• Material Effects
  • Corrosion of buildings, statues, and vehicles.